Another vote for Real Techniques blush brush! Definitely fluffly and super super soft!
I also like the Sephora Pro Domed Blush Brush, same shape as Real Techniques but a bit denser with plushy natural hairs:
I'm a blush blender so I like the two above. For more precision in application, I sometimes use my Sephora Pro Angled Blush Brush:
That looks like a great brush!
If you tend to be heavy handed with blush (I am!) try one with a longer handle- these help you get a lighter and more precision application on the face. I love Bobbi Brown for those:
Another great one I like is the Sephora Collection Angled Blush brush. It's slightly easier to use for contouring and defining on the complexion:
I recently got the Bobbi Brown blush brush after debating back and forth for a long time, it is beyond worth it, I love it! I also like the Sephora Pro angles blush brush 49 and MAC 168.
ECO TOOLS!!! I love love love this line of brushes.
1. They are so great to use with liquid, cream, and powder makeup. Blending and applying is effortless!
2. The feel so soft on my skin and don't irritate my face. There is no bristle fallout, unless I yank the bristles off myself, they are staying put.
3. The design is cute, the price is great, and they are easily accessible at; Ulta, Target, and drugstores.
4. Guilt free shopping, you know what you are getting is kind to the environment.
Here's a helpful thread that can cover styles of brushes for blush, it can help you narrow your search down depending on how you want product applied and then sort through brands that way!